1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly, to a method of forming a metal line of a semiconductor device.
2. Description of the Related Art
A related art method of manufacturing a semiconductor device will be described below with reference to FIGS. 1A to 1C.
Referring to FIG. 1A, an oxide is coated on a substrate 12 to form an inter-metal dielectric (IMD) 14. A photoresist pattern (not shown) is formed on the IMD 14 and a predetermined portion of the IMD 14 is etched to form a via hole 16a. A via plug 16 is formed by filling the via hole 16a with tungsten (W) using a chemical vapor deposition (CVD) process. Then, the surface of the via hole 16 is polished using a chemical mechanical polishing (CMP) such that an excessively deposited tungsten is removed.
Referring to FIG. 1B, aluminum (Al) is deposited on the via plug 16 and a metal line pattern 18 is formed, thereby forming a metal line of the semiconductor device.
Referring to FIG. 1C, a metal oxide 19 such as tungsten oxide (WOx) is formed between the via plug 16 and the metal line layer 18. The metal oxide 19 can be easily formed by the reaction of the metal (such as tungsten) existing on the surface of the via plug 16 with oxygen under air exposure after a CMP process of the via plug 16 or between the CMP process and the process of forming the metal line layer 18. Since the metal oxide 19 is formed between the via plug 16 and the metal line layer 18 deposited later, a contact resistance is degraded. Consequently, the reliability of the semiconductor device is degraded.